停止Applet的双缓冲Java小程序闪烁(stop applet flickering with

抱歉让问我的程序的问题，但我觉得我几乎没有，我自学java的，所以请大家多多包涵。我创建移动羊物体在屏幕上随机方向时，一只狗物体移动靠近羊的小程序。获取随机方向移动羊采取了一些工作，并与你们这里上的帮助，现在的工作（在某种程度上），但我想要现在要做的就是从闪烁停止它，当我在屏幕上拖动对象。我读过有关双缓冲，我可以得到它的一个主类的paint方法绘制的项目工作，但不能让它为被定义为独立的类单独的对象我的羊和狗对象。任何帮助都感激不尽。这里是我的代码：

    package mandAndDog;

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;


public class SheepDog extends Applet implements ActionListener, MouseListener, MouseMotionListener
{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    /**
     * 
     */

    Dog dog;
    Sheep sheep;
    int[] directionNumbersLeft = {0, 1, 3};
    int[] directionNumbersUp = {0, 1, 2};
    int x;
    int selection;
    int xposR;
    int yposR;
    int sheepx;
    int sheepy;
    int sheepBoundsx;
    int sheepBoundsy;
    int MAX_DISTANCE = 50;
    int direction;
    int distance;
    Boolean sheepisclosetodog;


    public void init()
    {
        addMouseListener(this);
        addMouseMotionListener(this);
        dog = new Dog(10, 10);
        sheepx = 175;
        sheepy = 75;
        sheep = new Sheep(sheepx, sheepy);
        sheepBoundsx = 30;
        sheepBoundsy = 30;
        direction = (int)(Math.random()*4); 
        distance = (int) (Math.random() * MAX_DISTANCE) % MAX_DISTANCE;
        sheepisclosetodog = false;
        Random rand = new Random();
        x = rand.nextInt(3);
        selection = directionNumbersLeft[x];

    }
    public void paint(Graphics g)
    {
        dog.display(g);
        sheep.display(g);
        g.drawString(Integer.toString(distance), 85, 100);
        g.drawString(Integer.toString(direction), 85, 125);
        g.drawString(Integer.toString(selection), 85, 140);

    }
    public void actionPerformed(ActionEvent ev)
    {}
    public void mousePressed(MouseEvent e)
    {}
    public void mouseReleased(MouseEvent e)
    {}
    public void mouseEntered(MouseEvent e)
    {}
    public void mouseExited(MouseEvent e)
    {}
    public void mouseMoved(MouseEvent e)
    {
    }
    public void mouseClicked(MouseEvent e)
    {}
    public void mouseDragged(MouseEvent e)
    {
        dog.setLocation(xposR, yposR);
        sheep.setLocation(sheepx, sheepy);
        if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
                && yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 0){
            sheepx = sheepx + 50;
            direction = (int)(Math.random()*4); 
        }
        if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
                && yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 1){
            sheepy = sheepy + 50;
            direction = (int)(Math.random()*4); 
        }

        if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
                && yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 2){
            sheepx = sheepx - 50;
            direction = (int)(Math.random()*4); 
        }
        if (sheepx <= 5){
            direction = directionNumbersLeft[x];
        }


        if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
                && yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 3){
            sheepy = sheepy - 50;
            direction = (int)(Math.random()*4); 
        }
        if (sheepy <=5){
            direction = directionNumbersUp[x];
        }

        xposR = e.getX();
        yposR = e.getY();
        repaint();

    }
}

class Dog 
{
    int xpos;
    int ypos;
    int circleWidth = 30;
    int circleHeight = 30;

    public Dog(int x, int y)
    {
        xpos = x;
        ypos = y;

    }

    public void setLocation(int lx, int ly)
    {
        xpos = lx;
        ypos = ly;
    }

    public void display(Graphics g)
    {
        g.setColor(Color.blue);
        g.fillOval(xpos, ypos, circleWidth, circleHeight);
    }       
}
class Sheep
{
    int xpos;
    int ypos;
    int circleWidth = 10;
    int circleHeight = 10;

    public Sheep(int x, int y)
    {
        xpos = x;
        ypos = y;

    }

    public void setLocation(int lx, int ly)
    {
        xpos = lx;
        ypos = ly;
    }

    public void display(Graphics g)
    {
        g.setColor(Color.green);
        g.fillOval(xpos , ypos, circleWidth, circleHeight);
        g.drawOval(xpos - 20, ypos - 20, 50, 50);
    }


}

首先，我不明白究竟为什么你有你的羊和狗类中的显示方法。相反，这样做的，我建议你显示你的牧羊犬类中羊和狗。

此外，而不是使用图形，你应该使用的Graphics2D。为了使用这个简单做

public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
}

这是可能的，因为Graphics2D的是显卡的一个子类。一旦你这样做，我会做的是重写update（）方法，并做到这一点

public void update(Graphics g) {
    if (image == null) {
        image = createImage(this.getWidth(), this.getHeight());
        graphics = image.getGraphics();
    }
    graphics.setColor(getBackground());
    graphics.fillRect(0,  0,  this.getWidth(),  this.getHeight());
    graphics.setColor(getForeground());
    paint(graphics);
    g.drawImage(image, 0, 0, this);
}

当你调用重绘（），它实际上首先调用update（）方法，这反过来又调用paint（）方法。在课程上，你应申报